Verapamil improves left ventricular (LV) diastolic filling in many pts with hypertrophic cardiomyopathy. To assess the effect of verapamil on simultaneious pressure volume (PV) relations, we generated high temporal resolution PVC loops using a micromanometer catheter and a non-imaging ECG-gated scintillation probe in patients before and after intravenous verapamil. Preliminary data suggest that verapamil-induced improvement in rapid diastolic filling of the LV is associated with improved isovolumic relaxation and late disatolic PV relations.